Keep the unit off. When a device gets water in it it is not the water that actually damages the device it is the dissolved solids and metals in the water that cause shorts in the circuitry.
Unfortunately the dock connector is connected to the logic board unlike the iPhone where it is a separate assembly.
You could try using a toothbrush to clean the pins inside the dock connector. Then use rubbing alcohol and a q-tip to clean it more throughly. Repeat this twice then try to charge it again.
If this does not work this means the logic board has become damaged and needs to be replaced.
-I would suggest selling it on eBay with an exact description of the issue.
-Or you could replace the logic board yourself which will be costly.